Improvement in galvanometers



w; E. DAVIS.

Gaivanomet-ers.

Patented Sept. 1,1874.

WILLIAM E. DAVIS, QF JERSEY GITY, NEW JERSEY.

PROVE MENT IN GLVANOMETERS.

' Specification forming part of. Letters PatentNo. 154,58,datedSeptember 1,1874; application filed March 5, 1874.

To all whom it may concern: 7

Be it known that I, WILLIAM DAVIS, of

7 Jersey City, in the county of Hudson and State of New Jersey, haveinvented a new and Improved Galvanometer -Coil, of which the followingis a specification:

Figure l-is a topview, partly in section, of

my galvanomcter-coil. Fig. 2 is a vertical central section of theinstrument, showing the coil in side elevation; and Fig. 3, a side viewof a modified form of the coil.

Similar letters of reference indicate corresponding'parts in all thefigures,

The object of this invention is to produce a' sensitive galvanom'eter,in which a single coil will answer every purpose of operating theneedle, and in which every one of the convolutions will, under theinfluence of a current,

necessarily, that one convolution of each coil must be laterally nearerthe needle than the remaining convolutions. A defect in the operation ofthe instrument thus constructed is necessary, as the convolution nearestthe magnet will alfect it more than that which is farther away from it.

Now, my invention consists in so arranging the convolutions of the wirearound the block or supporting-core of the coil that all the coinvolutions cross eachother at one point, which is directly underneath theneedle, so that a current flowing through the coil will, during itspassage through each convolution, aii'ect the needle, thus producing aharmonious and very pronounced effect on the needle.

In fact I have ascertained, bypractical experiment, that an instrumentwith but two or three hundred convolutions will be so sensitive as tocause a deflection of the needle when a drop of water is placed on oneof the bindingposts, and a piece of zinc from the other binding-postdipped in such water.

In the drawing, 1 first refer to Fig. 3, which best shows my system ofarrangement, the same bcin g the -representation of a sphere, amo gwhich the convolutions of wire are wound, so that each convolutionextends from pole to pole of the sphere, one of the poles, a, beingdirectly beneath the pivot of the needle I). There is, therefore, not,as in former instruments, one convolution, or a'series of con-Volutions, laterally nearer 'to the needle than the remaining:convolutions, and the object heretofore mentioned is thus fullyattained by my invention.

:But the spherical form of the coil is not an absolute necessity, as thesame principle of invention may be used on a cylindrical block, asindicated in Fig. 2, or on a block of other suitable form, theconvolutions extending on a cylindrical block along the sides of th'ecylinder, parallel to the axis thereof, and crossing over the heads orends of the cylinder, so that they will all meet at the poles, as shown.

In order to avoid the slight elevation at the poles by the thickness ofthe wires; crossing each other there, the core or block on which thewires are wrapped may be slightly depressed at the ends, so that finallythe entire coil will be flush at the ends. But this is a matter of meremechanical choice.

The needle b will besupported on a pivot, 61, that rests on a graduateddisk, A, under which the coil B is placed, and the ends of theconvolutions of the coil are connected to binding-posts e fiand thenceto the ground and to the battery, or to the material to be tested, asmay be desired. 7 Y

By any instrument of this construction,'the least variation ofconductive capacity can be observed, and it will, therefore, be of greatadvantage in testing the conducting power of plants and animal andvegetable matter of could be made heretofore.

In ordei to balance the instrument-that is to say, to bring it in suchexact position that the same power of current coming from one directionwill deflect the needle exactly as much as the same power of the currentwill various kinds much better than such tests deflect it when comingfrom the opposite di-' rection[ place the coil B on the supportingplate9 of the inclosing-case C, so that it can be turned, a suitable screw orpin, h, extending from the coil through the bottom 9, s0

Hunt by means of a screw-driver 01" other intions cross each ollmr at.the polcn', beneath strument; the coil may be slightly turned nn-' thecenter of the needle, substantially as detil the requisite balance. isobtained, mnkblmn scribed.

it; will be always in the right position for any WILLIAM EDWARD DA-VI'S.

l' VVihmssos: g' 1 claim as my invention- F. V. 'Bmmsnn, i Agalvanometercoil, ll), \vllpse convolu- A. V,. BRIESEN.

